Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, generator, gearbox, nacelle, and one or more rotor blades. The rotor blades capture kinetic energy from wind using known airfoil principles and transmit the kinetic energy through rotational energy to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
To ensure that wind power remains a viable energy source, efforts have been made to increase energy outputs by modifying the size and capacity of wind turbines. One such modification has been to increase the length of the rotor blades. However, as is generally understood, the loading on a rotor blade is a function of blade length, along with wind speed and turbine operating states. Thus, longer rotor blades may be subject to increased loading, particularly when a wind turbine is operating in high-speed wind conditions.
During the operation of a wind turbine, the loads acting on a rotor blade are transmitted through the blade and into the blade root. Thereafter, the loads are transmitted through a pitch bearing disposed at the interface between the rotor blade and the wind turbine hub. Typically, conventional pitch bearings include two rows of balls concentrically disposed within separate raceways defined between inner and outer races, with each ball being configured to contact its corresponding raceway at four separate contact points. Under ideal loading conditions, the loads transmitted through the pitch bearing are distributed evenly over all of the balls. However, due to dynamic loading on the pitch bearing and the difference in stiffness between the hub and the rotor blade, only a small percentage of the balls actually end-up carrying the loads during operation of the wind turbine. As a result, the stresses within such load-carrying balls tend to exceed the design tolerances for the pitch bearing, leading to damage and potential failure of the pitch bearing. Moreover, under dynamic loads, the balls of conventional pitch bearings tend to run up and over the edges of the raceways, resulting in the balls having reduced contact areas with the raceways. This leads to an additional increase in the stresses within the balls, thereby further increasing the potential for damage to the pitch bearing components. Similar issues are also present in conventional yaw bearings for wind turbines.
Accordingly, an improved bearing configuration that addresses one or more of issues described above would be welcomed in the technology.